A 53-year-old man described as being mentally ill was shot and killed by Fremont police early Sunday after a confrontation with police, the second fatal officer-involved shooting in Alameda County in three days.

The most recent incident happened about 6:45 a.m. Sunday, when Fremont police received a 911 call from a woman who said that her mentally ill adult son was "throwing things, turning furniture upside down and had thrown a piece of furniture out a window" at a home on the 400 block of Ohlones Street in the city's Mission San Jose neighborhood, authorities said.

The woman told a dispatcher that her son was armed with a knife and was stabbing a door. Three family members were inside the home at the time of the call, and two of them, the man's mother and brother, were stabbed by the suspect, police said. Their injuries were not life-threatening.

Officers arrived and evacuated the two injured relatives from the home, but the man's elderly father couldn't get out because of a medical condition, police said. Police entered and were "confronted by the suspect," authorities said without elaborating.

Two officers opened fire, killing the man.

Police withheld the names of the man and the officers but said both officers have been with the department for seven years and have previously served with other law-enforcement agencies. The two were placed on paid administrative leave pending investigations by police and the district attorney's office.

Prosecutors are also reviewing a separate fatal shooting of a robbery suspect by an Alameda County sheriff's deputy in Castro Valley.

The suspect, whose name was not immediately released, was shot inside Boulevard Burger at 3714 Castro Valley Blvd. at about 10 p.m. Friday, an hour after the restaurant had closed for the evening.

The incident began when a masked gunman, dressed all in black and carrying a loaded .357 revolver, entered the restaurant and demanded cash from a female employee. At the time, two male workers were outside collecting patio furniture and noticed two sheriff's deputies conducting an unrelated traffic stop nearby, said sheriff's Sgt. J.D. Nelson.

The male workers walked back inside the restaurant and were confronted by the robber, who ordered them to open the safe, Nelson said. The male workers yelled at their female colleague to hail the deputies outside and began struggling with the gunman, with one worker punching him while the other had a "death grip" on the gun, Nelson said.

The female worker alerted the deputies. One of them shot the robber dead shortly after the assailant's gun discharged as a result of the worker struggling with the gunman, Nelson said.

No one else was shot. The employee who grabbed the suspect suffered minor powder burns caused by the gunfire, authorities said.

"These employees did something that's very heroic that worked out in this circumstance, and maybe the thought process is they knew the deputies were in front of the building," Nelson said, adding that the deputy's training enabled him to act quickly "in a very volatile situation, literally within seconds of walking in the door."

In a statement, restaurant officials said they were "truly grateful for the fast thinking and bravery of our employees and the officers from the Alameda County Sheriff's Office. Their valor prevented this tragedy from being any worse."

The incident is the fourth shooting involving the sheriff's office this year and the third in Castro Valley.

In March, deputies shot and killed suspects in Oakland and Castro Valley. Last month, a deputy shot and critically wounded a suspect who tried to drag another deputy with a car in Castro Valley.